The invention relates to a sliding system which is provided with a semi-spherical shoe, and more particularly, to a sliding system which is preferred for use as a semi-spherical shoe interposed between a piston and a swash plate of a swash plate compressor, for example.
The use of a semi-spherical shoe including a semi-spherical surface and a flat end face in a swash plate compressor is known in the art.
A semi-spherical shoe is known in the art in which a top end thereof is notched in a direction perpendicular to the axis to define a flat surface (see Japanese Laid-Open Patent Application No. 76,281/1982 and Japanese Laid-Open Utility Model Application No. 7, 288/1988). With this semi-spherical shoe, when the semi-spherical surface of the semi-spherical shoe is fitted into a semi-spherical recess formed in a piston, a space is defined between the semi-spherical recess and the flat surface located at the top end of the semi-spherical shoe and can serve as a reservoir for a lubricant oil.
In the conventional semi-spherical shoe, a sliding contact region which is disposed in sliding contact with the semi-spherical recess in the piston is defined by part of the semi-spherical surface located between the flat surface at the top end of the semi-spherical surface and the end face.
However, in the construction of the conventional semi-spherical shoe, part of the semi-spherical surface which is located above the sliding contact region has the same diameter as the remainder of the semi-spherical surface, and accordingly, the arrangement is substantially not adapted to provide a clearance between the semi-spherical surface above the sliding contact region and the semi-spherical recess in the piston. Accordingly, if a reservoir of lubricant oil is maintained in a space formed between the semi-spherical recess and the flat surface at the top end of the semi-spherical shoe, the lubricant in the space is less susceptible to being guided into the sliding contact region disadvantageously, which explains for a poor sliding response of the conventional semi-spherical shoe.
In view of the foregoing, according to the present invention, there is provided a sliding system including a first movable member having a semi-spherical recess, a second movable member having a flat surface, and a semi-spherical shoe having a semi-spherical surface which is fitted into the semi-spherical recess of the first movable member and an end face disposed in sliding contact with the flat surface of the second movable member wherein a sliding contact region which is disposed in sliding contact with the semi-spherical recess is defined between the top and the end face of the semi-spherical surface, with a region of the semi-spherical surface which is located above the sliding contact region being a lead-in so that when the semi-spherical surface is fitted into the semi-spherical recess, a clearance is defined between the lead-in and the opposing portion of the semi-spherical recess which gradually increases toward the top of the semi-spherical surface.
With this arrangement, the clearance defined between the lead-in and the opposing portion of the semi-spherical recess allows a lubricant oil which is stored in the space between the semi-spherical recess and the top portion of the shoe to be introduced into the sliding contact region through the clearance. In this manner, there is provided a sliding system having an excellent sliding response as compared with the prior art.